Method of making sound reproducing diaphragms



9 I J. B. HAWLEY 2,017,496

METHOD OF MAKING SOUND REPRODUCING DIAPHRAGMS Original Filed-Dec. 24, 1930 Patented 0a. 15, 1935 UNITED STATES METHOD OF MAKING SOUND REPRO- DUCING DIAPHRAGMS Jesse B. Hawley, Geneva, Ill. Original application December 24, 1930, Serial-No.

504,536. Divided and this application June 18, 1934, Serial No. 731,074

7 Claims; (o1. 181-32) The present invention relates to the reproducing diaphragms'.

Among the objects of the invention is to provide a novel method of producing or making sound reproducing diaphragms or diaphragmatic members.

To obtaina sound producing or reproducing diaphragm capable of producing or reproducing sound true and faithful to the original'sound to be reproduced, it is necessary that the dia phragmatic member be as light in weight aspossible and not subjected to a natural period or fundamental frequency, yet sufliciently stiff to set up'the proper waves in the sound medium.

An object of the invention is to so produce such a sound producer or reproducer as will have a substantially even response curve, where all sounds of the audible range will be produced or reproduced with substantially equal efficiency.

In an illustrative embodiment of the invention the sound producer or reproducer is preferably of molded fibrous material. It is made in one single piece and without any seam. It may be of any desired shape, as pyramidal, cone shaped, conoidal, cissoidal and other similar shapes, with an integral basal flange by which the diaphragmatic member may be supported. It is-very thin and very light in weight to' reduce to a minimum the mass inertia or momentum thereof. The

art of sound flange is preferably made with a border portion for retention by a support or holding means, and a thinner portion between the border portion and the body part of the device, whereby the freedom of vibration of the sound producer may be greatly enhanced, the thinner portion mentioned being very easily flexed or, having increased flexure. This portion is also preferably undulated to aid the pliability or fiexure at the cated.

This thinner portion may be and preferably is eflfected by compressing or compacting the fibrous material at the juncture between the bodyportion' or cone part of the diaphragmatic member, and the basal flange. In the process of molding, the fibres are preferably deposited on a porous former to form a blank' The thickness of the deposit is substantially uniform throughout the blank. The blank, either while still wet or moist, or after it is dried, is then subjected to compression; as between dies, or rollers, or the like, for compressing or compacting the fibres at the region mentioned. If desired, the whole diaphragmatic member may be calendered or compressed to compact the fibres,

region above indipurpose above mentioned. Or, if desired, the member may be left uncompressed or 'uncalendered.

Another object of the invention is to impregnate the sound producer with moisture or water proofing material or substance, whereby the acoustic prop- I erties of the diaphragm will not change with the humidity of the sound medium, such as the air of the atmosphere. The impregnation may be of different degrees over the diaphragm, so that different parts of the diaphragm may be efilciently responsive to the different periods of the audible range of sound to the end of making the diaphragm substantially non-fundamental in periods.

A further object is to provide a novel process of making such a diaphragm as by depositing the fibres of a bath on a porous former, applying pressure on the part of the fibrous blank to be made thinner for flexure, with or without impregnating 20 the blank, and finishing, as by drying, compressing and the like. The pressing may be effected while the blank is wet, or after theblank has been dried, or after the blank has been treated.

Other objects, advantages, capabilities, features and process steps are comprehended by the enlarged scale through the compressing means.

and the compressed portion of the diaphragmatic member. l

Fig. 4 is a top plan view of a finished blank. Referring now more in detail to the drawing, the diaphragm constructed in accordance with the invention is made by depositing fibres upon a porous former I having pores or apertures 2, from a bath of fibrous material in a liquid such as water.

The former I, as in the illustrative construction,

is of any desired shape, and the particular shape of the blank to be moulded, has a cap 3 which may be either closed or porous asdesired, and a flange 4 which is also porous.

vided with anundulated or corrugated juncture portion 5. This former may fit into a container 6 of the bath. Within and below theformer a Between the flange and the body portion I the former ispreferably propartial vacuum may be created so that the liquid preferably is agitated and vibrated to maintain the fibres in suspended and dispersed condition, and also to aid in the proper laying and interlacing of the fibres deposited and accreted on the former.

After the blank has been completely formed in the manner above described, the blank may be removed from the former and placed upon a compressing member, such as a die 1" having the proper and desired configuration or contour as clearly shown in Fig. 2. It is preferable thatthis j compressing member have a counter part corresponding to the corrugated portion 5 of the former and to fit properly with the corrugated portion 8 of the blank. A second compressing member, such as a die 9 or a roller 9 having a counter part undulated or corrugated surface l or III, is made to engage with the opposite surface of the corrugated portion 8 of the blank as clearly shown in Figs. 2 and 3. The compressing members are then made to function so as to compress the fibrous material therebetween for the purpose of compacting such fibres and also to render the thickness of the compressed portion of the fibres less than the body portion II and the flange portion l2 of the diaphragmatic member. In this way the compressed juncture will be made more durable and lasting although the same is made more pliable and flexible by reason of making the material thinner than the body and flange of the blank. By making the juncture also'undulated 0r corrugated, the flexibility or pliability of the juncture is enhanced.

If desired, before the compression of the juncture is effected the whole blank may be compressed to compact the fibres, and the juncture given an additional pressure or compression to effect the desired thinner and tougher portion as above described. It is preferable to treat the blank either when it is soft and wet or after ithas been dried, with some impregnating material which has moisture ingly.

or water proofing properties. As for example, the apical or central portion of the diaphragm or cone may be impregnated with such substances I as duco, lacquer or like similar substances. The

remainder of the diaphragm may be impregnated the diaphragm. The basal flange portion may be impregnated with such material as rubber cement, latex and other like and similar materials. The impregnation may vary over different areas so that the stiffness and flexibility may vary accord- Ifdesired, the impregnating material might be mixed in the pulp bath so that when the fibres are deposited, they will also carry with them the proofing material. Such material as asphaltum,

latex, resin, size and sulphate or aluminum may be used. These may help to toughen and water proof the material of the diaphragm so that the diaphragm will have the desired acoustic characteristics mentioned above. Any may be used:

The diaphragm is of extremely light weight, and very flexible in the flange portion thereof,

kind of fibre particularly at the thin portion or juncture between the cone or body portion andthe flange portion.

In use a hollow cylinder is attached to the neck l6 and carries a coil of fine wire located in an annular magnetic gap of a dynamic type of actu- 10 ator. The border I2 is clamped in a fixed part of the sound reproducing mechanism, so that the diaphragm or cone is suspended byway of the thin corrugated juncture 8 of the diaphragmatic member. nected at the neck portion l6 for movably supporting that end.

As the cone portion is vibrated, the thin corrugated band or juncture 8 permits its freedom of vibration by reason of the thinness and un'- dulatory form of that portion thus giving great flexibility and pliability at the parts located be- .tween the flange I! which is held in fixed position and the moving cone or body I of the diaphragmatic member. 4

In this art, difficulties are met in which a -diaphragm of this kind usually has some fundamental period or natural frequency of vibration at which some waves of the sameperiod will be more efiiciently rendered or reproduced than others of-the audible range. In making a portion of the diaphragm stifier than another portion, certain frequencies of the audible range will be more efficiently transmitted or emitted by the stiffer portion, while the other frequencies will be more efiiciently transmitted by the less stiff portion of the diaphragm. As for example, if the diaphragm be of low natural period tendency, it would tend to reproduce low frequencies more efficiently. By stiffening a portion, that portion 40 will transmit certain frequencies, such as the high frequencies, more efiiciently, and by making other portions more flexible, the latter portions will transmit other frequencies, such as low frequencies, more efiiciently. In this way the whole 4 audible range may be efliciently reproduced.

By making the diaphragm of integral material, such as moulded fibrous substances, certain disadvantages are avoided, such as those that are present in the rolled and seamed cone, or the stretched cone. In the latter forms, the material used is placed under strains and stresses which affect the acoustic properties of the sound reproducer. By the present invention, the shape of the diaphragm is that originally produced and I; there is no strain nor stress of any kind to affect its acoustic properties. The compressing of the connecting portion or band between the cone and the flange does not produce a distortion or stress or strain in the body portion of the cone from which the sound waves are sent forth in the sound transmitting medium, such as the atmosphere. Moreover, the diaphragm of the present invention is more or less porous even after it is 'it' is to be understood that the invention is not limited to the particular steps or acts of the II Suitable flexible means may be con- 15 aormee process stated, but may comprehend other process steps and features without departing from the spirit of the invention.

Having thus disclosed the invention.

I claim:

1. In a process of making molded fibrous dia phragmatic sound producers, the steps of forming a blank on a porous former, and compressing a portion of the formed blank to make said portion thinner and more compact than the remainder of said blank.

2. In a process of making molded fibrous diaphragmatic sound producers, the steps of forming a blank on a porous former with an undulated portion in said blank, and compressing said undulated portion to make it thinner and more flexible than the remainder of said blank.

3. In a process of making molded fibrous diaphragmatic sound producers, the steps of forming a blank on a porous former, compressing a portion of the formed blank to make said portion thinner and more compact than the remainder of said blank, and impregnating said blank with moist\ e proofi. material.

4. In a process of making molc-d fibrous-diaphragmatic sound producers, the steps of forming a blank on a porous former with an undulated portion in said blank, compressing a portion oi the formed blank to make said portion thinner and more compact than the remainder of said blank, and impregnating said blank with moisture proofing material.

5. In a process of making molded fibrous dia phragmatlc sound producers, the steps of forming a blank on a porous former, compressing a portion of the formed blank to make said portion thinner and more compact than the remainder of said blank, impregnating the central portion of said blank with a moisture proofing and stifiening substance, and impregnating the remainder of said blank with a moisture proofing supple producing substance.- r

6. In a process or making molded fibrous diaphragmatic sound producers, the steps of form:

ing a blank on aporous former with an undulated 15 portion in said blank, drying the blank, and compressing said undulated portion to make it thinner and more flexible than the remainder of said blank.

'1. In a process of making molded fibrous diaphragmatic sound producers; the steps of forming a blank on a porous former with an undulated portion in said blank, drying the blank, compressing said undulated portion to make it thinner and more flexible than the remainder of said a blank, and impregnating said blank with moisture proofing material.

JESSE B. HAWLEY. 

